1. Field
This disclosure relates to a partial discharge detection sensor and a partial discharge detection device using the same, and more particularly to a partial discharge detection sensor which is located in a gas-insulated device to detect a partial discharge signal occurring in the gas-insulated device, and a partial discharge detection device using the same.
2. Description of the Related Art
Power equipments such as gas-insulated power transmission lines, gas-insulated switches, gas-insulated transformers, gas-insulated buses and bus ducts are gas-insulated equipments configured such that an insulating gas is filled in a grounded enclosure and also a conductor is insulated by a solid insulator and supported in the enclosure.
In the gas-insulated equipment, partial discharge may occur due such factors such as impurities existing in the gas-insulated equipment, internal defects like scratches or projections of the inner side of the enclosure or the inner conductor, or inaccurate assembly.
The partial discharge has a great influence on the performance of the gas-insulated equipment, which may cause a catastrophic accident if left alone. Thus, there is a need of a device for finding out a partial discharge early by measuring and detecting the partial discharge by a signal of an electromagnetic form such that a countermeasure can be taken rapidly.
As one of existing devices and methods for detecting a partial discharge in a gas-insulated equipment, there is a device and method for detecting a partial discharge using an external sensor installed at an outside of the gas-insulated equipment.
FIG. 1A is a plan view showing the concept of the device and method for measuring a partial discharge by installing an external sensor at an outside of a gas-insulated equipment, and FIG. 1B is a sectional view showing the device of FIG. 1A.
As shown in FIG. 1A, the external sensor 11 is installed at an outside of an enclosure 20 that constitutes a gas-insulated equipment 1. In this method, a partial discharge signal transmitted through a spacer 21 that fixes and supports an inner conductor in the enclosure is detected. Referring to FIGS. 1A and 1B, a sensor box 10 made of a metal plate is installed at a shielding metal band 22 that shields and surrounds the spacer 21, and a sensor 11 is installed therein. A partial discharge signal occurring due to internal defects such as projections 41 is transmitted to the sensor passing through a dielectric substance that constitutes the spacer 21.
However, the partial discharge detection device using such an external sensor 11 has low sensitivity, and particularly it is seriously influenced by external noise.
To solve this problem, there is proposed a method in which a sensor is installed inside the gas-insulated equipment. In this method, ultra high frequency (UHF) sensors are frequently used.
FIG. 2 is a schematic view showing the concept of the device and method for measuring a partial discharge by installing a UHF sensor in the enclosure of a gas-insulated equipment.
As shown in FIG. 2, the UHF sensor 10 is generally installed inside a disk 50, frequently called a monitoring window, to detect a partial discharge signal occurring in the gas-insulated equipment 1. Generally, the UHF sensor 10 used in such a device is formed by disposing a conductor line on the disk 50 and then pouring epoxy or the like thereto. Thus, it is difficult to make the UHF sensor 10 into various shapes, so the UHF sensor 10 may not be easily produced to have a broadband detection characteristic. Thus, in general, the UHF sensor 10 for detecting a partial discharge signal has ultra high frequency band in the level of several GHz.
Among partial discharge signals occurring in the gas-insulated equipment, partial discharge signals occurring at long distances include all signals from low frequency band to ultra high frequency band. However, a signal in the level of ultra high frequency band (several GHz) is attenuated rapidly during transmission, although it has a great intensity when it is generated, while signals in high or low frequency bands are relatively less attenuated. In other words, it is required to use a sensor having a broadband characteristic in order to effectively detect partial discharge signals occurring from the inside of the gas-insulated equipment.
Although the device and method for measuring a partial discharge by installing a UHF sensor in the enclosure of a gas-insulated equipment may decrease noise occurring out of the gas-insulated equipment, the UHF sensor generally has a ultra high frequency band as mentioned above. Thus, this device and method exhibits bad sensitivity when receiving and detecting a partial discharge signal occurring at a long distance.